1. Field of the Invention
The present invention relates to a field effect transistor for controlling the formation of a channel by the application of a voltage to a gate electrode and a method of manufacturing the same.
2. Description of the Related Art
An example of a field effect transistor of a double gate structure in the related art is shown in FIG. 15. In this existent embodiment, n type or p type source/drain regions 13a and 13b are formed on both sides of an n.sup.--, p.sup.--, or i type channel region 12 of a semiconductor layer. Gate electrodes 15a and 15b are disposed on both upper and lower surfaces of the channel region 12 by way of gate insulation layers 14a and 14b.
The field effect transistor described above has been manufactured in the related art by epitaxially growing the semiconductor layer 11 on the gate insulation layer 14a by a so-called lateral solid phase epitaxial growth, introduction of an impurity selectively into the semiconductor layer 11 thereby forming the source/drain regions 13a and 13b.
In the field effect transistor of the related art embodiment shown in FIG. 15, since an electric field can be applied from both of the gate electrodes 15a and 15b to the channel region 12, the number of carriers induced in the channel region is greater and the current driving performance and the mutual conductance are higher as compared with a single gate structure.
Further, various characteristics can be attained easily, without introducing impurities into the channel region 12, by operating the gate electrodes 15a and 15b independently of each other and, for example, applying a bias to the channel region 12 on one side of the gate electrodes 15a and 15b.
However, since the power source voltage has been lowered along with miniaturization of the field effect transistor, the current driving performance and the mutual conductance are no more sufficient even in a field effect transistor of the double gate structure in the related art embodiment shown in FIG. 15. Further, since the crystallinity of the semiconductor layer 11 formed on the gate insulation layer 14a by the lateral solid phase epitaxial growth is incomplete, it was difficult to manufacture a field effect transistor having high carrier mobility and high speed operation.